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#!/usr/bin/env python
# -*- coding: utf-8 -*-
from __future__ import unicode_literals, print_function, absolute_import
import six
import random
from django.db import models
import logging
import traceback
class ITableChunk(object):
def __iter__(self):
raise NotImplementedError
def get_pk_start(self):
raise NotImplementedError
def get_pk_stop(self):
raise NotImplementedError
class TableScannerChunk(ITableChunk):
def __init__(self, data_list, pk_start, pk_stop):
self._data_list = data_list
self._pk_start = pk_start
self._pk_stop = pk_stop
def __iter__(self):
return iter(self._data_list)
def get_pk_start(self):
return self._pk_start
def get_pk_stop(self):
return self._pk_stop
class TableScannerChunkIterator(object):
def __init__(self, scanner, last_pk, chunk_size):
assert isinstance(scanner, TableScanner)
self._scanner = scanner
self._last_pk = last_pk
self._chunk_size = chunk_size
def __iter__(self):
while True:
last_pk = self._last_pk
data_list, next_last_pk = self._scanner.get_next_data_list(last_pk=last_pk, chunk_size=self._chunk_size)
self._last_pk = next_last_pk
yield TableScannerChunk(data_list=data_list, pk_start=last_pk, pk_stop=next_last_pk)
class TableScannerFlattenIterator(object):
def __init__(self, scanner, last_pk):
assert isinstance(scanner, TableScanner)
self._scanner = scanner
self._last_pk = last_pk
def __iter__(self):
while True:
data_list, next_last_pk = self._scanner.get_next_data_list(last_pk=self._last_pk)
self._last_pk = next_last_pk
for data in data_list:
yield data
class TableScanner(object):
def __init__(self, queryset):
assert isinstance(queryset, models.QuerySet)
self._model = queryset.model
self._query = queryset.query
self._db_table = self._model._meta.db_table
@property
def queryset(self):
return models.QuerySet(model=self._model, query=self._query)
@property
def model_queryset(self):
return self._model.objects
def get_random_pk(self):
count = self.model_queryset.count()
if count == 0:
return None
index = random.randrange(count)
try:
return self.model_queryset.values_list('pk', flat=True)[index]
except IndexError:
return None
def get_next_data_list(self, last_pk=None, chunk_size=1):
qs = self.queryset.order_by('pk')
if last_pk is not None:
qs = qs.filter(pk__gt=last_pk)
data_list = list(qs[:chunk_size])
if len(data_list) == 0:
next_last_pk = None
else:
next_last_pk = data_list[-1].pk
return data_list, next_last_pk
def __iter__(self):
pk = self.get_random_pk()
return iter(TableScannerFlattenIterator(scanner=self, last_pk=pk))
def chunks(self, chunk_size):
pk = self.get_random_pk()
return iter(TableScannerChunkIterator(scanner=self, last_pk=pk, chunk_size=chunk_size))
class TableSlicerChunk(ITableChunk):
"""
this object can be pickled and transferred to another process.
"""
def __init__(self, model, query, pk_start, pk_stop):
self._model = model
self._query = query
self._pk_start = pk_start
self._pk_stop = pk_stop
def __iter__(self):
data_list = self.__get_range(self._model, self._query, pk_start=self._pk_start, pk_stop=self._pk_stop)
return iter(data_list)
def get_pk_start(self):
return self._pk_start
def get_pk_stop(self):
return self._pk_stop
@classmethod
def __get_range(cls, model, query, pk_start, pk_stop):
qs = models.QuerySet(model=model, query=query)
if pk_start is not None:
qs = qs.filter(pk__gte=pk_start)
if pk_stop is not None:
qs = qs.filter(pk__lt=pk_stop)
return list(qs)
class TableSlicer(object):
def __init__(self, queryset, chunk_size=None, chunk_count=None, sep_list=None):
try:
assert isinstance(queryset, models.QuerySet)
assert chunk_size is None or isinstance(chunk_size, six.integer_types)
assert chunk_count is None or isinstance(chunk_count, six.integer_types)
assert sep_list is None or isinstance(sep_list, list)
assert (chunk_size is not None) + (chunk_count is not None) + (sep_list is not None) == 1
if sep_list is not None:
sep_list = list(sep_list)
else:
count = queryset.count()
if chunk_size is None:
chunk_size = count / chunk_count
index_list = list(range(0, count, chunk_size))
sep_list = [
queryset.order_by('pk').values_list('pk', flat=True)[index]
for index in index_list
]
self._model = queryset.model
self._query = queryset.query
self._sep_list = [None] + sep_list + [None]
except:
logging.error("catch exception,err_msg:%s" % traceback.format_exc())
def chunks(self):
try:
reversed_sep_list = list(reversed(self._sep_list))
logging.info("duan add,reversed_sep_list:%d" % (len(self._sep_list) - 1))
for i in range(len(self._sep_list) - 1):
pk_start = reversed_sep_list[i + 1]
pk_stop = reversed_sep_list[i]
yield TableSlicerChunk(model=self._model, query=self._query, pk_start=pk_start, pk_stop=pk_stop)
except:
logging.error("catch exception,err_msg:%s" % traceback.format_exc())
class TableStreamingSlicer(object):
def __init__(self, queryset, chunk_size=None):
assert isinstance(queryset, models.QuerySet)
assert chunk_size is None or isinstance(chunk_size, six.integer_types)
self._model = queryset.model
self._query = queryset.query
self._chunk_size = chunk_size
self._descend = False
def chunks(self):
last_pk = None
queryset = models.QuerySet(model=self._model, query=self._query).order_by('pk')
value_list = queryset.values_list('pk', flat=True)
while True:
current_value_list = value_list
if last_pk is not None:
current_value_list = current_value_list.filter(pk__gt=last_pk)
try:
next_last_pk = current_value_list[self._chunk_size-1]
except IndexError:
next_last_pk = None
yield TableSlicerChunk(model=self._model, query=self._query, pk_start=last_pk, pk_stop=next_last_pk)
last_pk = next_last_pk
if last_pk is None:
break